Hello to all, I'm new here as a member, but have been reading here for the past the several months.

I have a question about turbo piping size because of space limitations.

For some background, we have a 9.1:1 327 SBC with a TPI from an '85 Vette being controlled by an MS2 in a Pontiac Astre with dual exhaust and ladder bars. We are gathering the parts to install a turbo behind the rear axle in the hole that used to carry the spare tire. We have picked up a T04B35 (cheap) and have a Tial wastegate and BOV. FWIW - when we started out on this plan with the turbo I had a lot of questions. I've found a ton of answers in old threads on this forum and then I stumbled across the 'grenade' thread, read it ALL in one night. It got me and my son hooked on the turbo giddyup. So, we are going to find out.

We are planning on using 2.5" piping into the intake, but it would be a lot easier, due to clearance limitations, to get over the rear axle and with 2" and then convert to 2.5" in front of the axle. Is that going to be a problem? If yes, then what is it going to create? Will it create higher intake temps?

As always, thanks in advance - Jim

 

Your plan for intake piping going from 2" to 2.5" is fine as long as the compressor outlet is no larger than 2" The smaller the total area of piping both on the intake and exhaust(to the turbo) the better system response you will have. With that said, if at all possible placing the turbo under hood will be better than rear mounted.

 

Thanks for the response. The compressor housing is 2" so we'll give it a try. In terms of putting the turbo under the hood, there isn't room, in my opinion, considering that the every attaching component is homemade or made up of pieces of kit for other applications, i.e. alternator and brackets, p/s pump & brackets, etc. Basically, the only part we bought that was designed for this car were the Sanderson headers.

 

That turbo is popular on V6s, and is almost certainly going to be too small. Putting an intake that is done by 4500rpm onto an engine that likes to rev never made sense to me either.

 

Where is your battery? In that car, it should be mounted in the rear anyway, to help with the strong front weight bias it will already have, and there should be enough room for a turbo where the battery was. If I were you, I'd delete the P/S, it's not really needed on that car, and move the alternator, if need be, to get the turbo up front. Trust me when I tell you, it will be MUCH easier to get that project finished with a front mounted turbo. Take a look at my project thread if you want some ideas for a different layout, it's a twin turbo Vega. Good luck, and if I can be of any help, let me know....

 

Rick,
The battery is in the trunk. In terms of deleting the p/s steering, will I be able to use the current steer gear, or will I have to convert to a rack? I have to admit that converting to a rack and pinion would be handy for space. I also have to admit though, the power steering is nice as well. I did see your thread and looked closely at your setup. It is pretty slick! I have to keep in mind though that this is a cruiser and not an all out strip car - 400 to 450 rwhp is more than enough for what this car is. And for that matter 350 at a minimum would be more than adequate for a tire burner. Keep in mind it is not back halved and the rear suspension is fair at best.

Monte,
The turbo might be small and might not work worth a crap, but it's what we have and we are going to try it. If it's a turd, then we'll do something different. In terms of a high revving 327, we also are running a rod to stroke ratio of almost a 2:1 which makes it want to rev even faster and higher which is contradictory to running a TPI, BUT considering we are running heads that are a little bit better than stock heads and the car is a driver, we thought we'd try this rear setup. I think this turbo is going to come in late, which is OK so that the cruise mileage shouldn't take to much of a hit. We currently get 20-21 on the highway and we are making 300 hp and 355 ft/lb torque (give or take some) at the crank. It did make more with a Holley and it got 11 mpg, hence, the reason for the TPI and also it is different.

Thanks for input.

 

Also forgot to mention that I ported the plenum and runners. In terms of out of go at 4500, that is stock setup. This thing maxed out at 5200 on a chassis dyno a month and half ago.

 

You can just get a manual box, they are quite popular with the street rod crowd, Flaming River even makes a brand new one, but you can find them used on http://forums.h-body.org/ now and then. I sold mine there a while back. I used to have a 73, and when it had a 327 in it, I used a mid 80s Corvette alternator bracket with a short pump, there would have been plenty of room for a turbo in there. That same car went 11.90s with the 327, and 9.70s with a 427 in it, with the "stock style" (heavily reinforced) 4 trailing arm suspension. There's a guy on the site I mentioned above that goes low 10s with a N/A 355 or 383 with a stock style suspension, he goes by Speedphreak.

 

Thanks for the info. I'm on the h-body forum also, I go by JimW. Did you ever run a single turbo setup on an H-body? If yes, how did you tie the exhaust together. In terms of belt drive system. I've homemade my alternator lower mounts that attach to the water pump bolts with a foot long adjuster to the top of CS100 alternator. The power steering pump is an adaptation of an AllStar performance bracket for a GM type II pump that is shimmed to hit my pulley that is off an early 80's sbc that uses both v and serp belts. It's kind of a mess, but looks pretty clean and has lasted for 4-5000 miles. And my wife can tell you how many spare (junkyard) parts we gathered to figure out the belt system. I've more pulleys, mounts, belts, and brackets than any part store in the area


Also, on another note, I just read the sticky about turbo basics in the DIY section - wow, that's is informative.

 

Nope, I've built a couple of turbo motors and helped tweak on a few cars over the years, but this is my first turbo combination of my own. I did pretty much EVERYTHING to this Vega I always wanted to do to the other one, short of going complete tube chassis. I may chop the front end off and finish the job one of these days, but if I can make enough power, and put it to the ground, to get it in the 8s, without breaking the bank, probably not....

- - - Updated - - -

Nope, I've built a couple of turbo motors and helped tweak on a few cars over the years, but this is my first turbo combination of my own. I did pretty much EVERYTHING to this Vega I always wanted to do to the other one, short of going complete tube chassis. I may chop the front end off and finish the job one of these days, but if I can make enough power, and put it to the ground, to get it in the 8s, without breaking the bank, probably not....

 

I kept my long tube headers on my car, and Y-ed them into a single 3 inch pipe back to the turbo.

 

393ci, Shorty headers to 2 1/4", then into a single 3", Cold side is 3" all the way. Turbo is Precision t76 with .96 exhaust A/R. 3 1/2" after the turbo. It spools up good, but I need to do some more tuning. Weather is getting to the point that I will have to put it up till spring soon.

Jess

 

Thanks for the reply. I appreciate your response as we are on a 'similar' program, other than the Ford vs. GM thing. What size is your turbo on the intake side? I'm going to do almost the same thing with the exhaust piping. We are running 2 1/2" off the shorty headers and I was going to merge them into a 3" to get over the axle and then run 2 1/2" back to the TB. Are you running mufflers?

Also, what are you controlling the EFI with?

X2 on the weather thing. 23 freaking degrees this morning. I spent the weekend fixing rusted parts (brake lines, spring hangers) on my beater to get throuh the winter :{

Jim

 

I have a question to all about the mufflers. Based on the idea that the turbo is going to quiet down the exhaust, we are considering eliminating the mufflers. For a little background, currently, this car is LOUD and my son would like it stay somewhat noisy. We are currently running 2 Cherry Bomb Extremes. From my standpoint, it would make the piping fabrication and mounting alot simpler if we lost the mufflers. My question is will the turbo quiet down the exhaust some, alot, or none? Anyone have much experience with this (someone must)?

 

Turbos do act as mufflers, they chop up the sound pulses with the turbine wheel. I would go without any mufflers just be sure the tail pipe is straight out the rear of the car if possible. Dumped under the car will make it loud in the cabin.

 

Mine is still really loud. I didn't have any room for an effective muffler, so I welded a flowmaster outlaw series collector muffler at the very end of the tail pipe. It doesn't really do anything though.

 

You might want to think about going under the axle with the 3". On my 427 Vega, I spent like 6 hours making (4) 2.5" tail pipes, coming off homebuilt mufflers, 3.5" inlets to dual 2.5" outlets on each muffler. When I was all done, standing behind the car on the lift, I had one of those forehead slapping moments, as I standing there looking at it, I realized I could have come straight off the mufflers UNDER the rear. Just a thought. With the twins on my current Vega, and with the exhaust only about maybe 4' long from exhaust port to 3" D/P tips, I think it's quiet enough to street drive it. With the smaller pipe sizes and additional length, I think you should be OK for sound.

 

I think you guys have talked me into eliminating the mufflers. I can always add a single later and the worst thing that will happen is it will be loud .

Rick,
I have read in several places about running the pipe(s) under the axle, but I was concerned about contact with axle if I try to keep the ground clearance at 4" or so. How much clearance should be needed between the pipe and the axle to safely eliminate contact?

 

Depends a lot on your suspension travel, but it's way easier to have just a little dip under the axle than a huge 180° over the axle, and being that the dip is in line with the rear wheels, ground clearance isn't such an issue with speed bumps and such. The only time suspension travel downward would be maxed out would be if you got airborne. On my car, 1" to 1.5" would have been plenty.

 

I don't recall the exact specs on my turbo. Discharge is 3" though. After trying to get the car to run the way I wanted to with a stock ford computer and a Moates tuner, I swapped in a Megasquirt II. The self tuning feature is awesome.

I use a 3 1/2" Dynomax Ultraflow muffler. It exits in the stock location on the drivers side. My wastegate dumps to a matching pipe on the passengers side. This is a thread I started about my rear mount experiences;

https://www.theturboforums.com/threads/357093-Rear-mid-mount-turbo-in-1990-mustang

I have been really slacking off lately. I wanted to get some paint on the car and finish adjusting the seals for the T-top, but never got around to it. I have been doing a bunch of drywall work on my house, the idea of going out and sanding on my car is not appealing to me.

Jess